which reaction results in the greatest increase in entropy

As catalysis only happens on the surface of metals, an increase in the accessible surface area would considerably improve the catalyst's efficiency, hence reducing its effective cost 32. Gold nanoparticles' catalytic activity is influenced by a number of factors, including their size, concentration, and temperature 30, 31. In general, when particle size decreased, catalytic activity increased 29. Size and shape-dependent nanocatalysis has emerged as an active research subject 27, 28. Physical and chemical characteristics of materials 23, 24 with a high surface-to-volume ratio 25, 26 are influenced by electron mobility. Gold nanoparticles possess peculiar features and have several uses in electronics, photonics, biological sensing, and imaging 21, 22. Large-scale commercial applications in catalysis involving reduction processes based on nanocages, nanoboxes, and nanoparticles 12, 13, 14, 15, 16, 17, 18, in bone malignancies treatment 19, and nanocarrier creation 20. Emerging therapies such as photothermal cancer therapy 7, electrochemical sensors 8, medicinal and health care uses treating COVID-19 9, and antimicrobial nanoparticles 10, 11 are only a few examples. Nanotechnology is one of the most versatile technologies because it can be used to create a wide variety of materials, including nanocomposites 1, 2, bimetallic nanoparticles 1, 2, 3, and quantum dots 4, all of which have applications as catalysts 5, 6. Besides being a model redox reaction, the reduction of K 3Fe (CN 6) −3 to K 4Fe (CN 6) −4 has industrial use in making fertilizers and paint industry, anti-coating agent in colour photography, in dot etching and in amperometric biosensors.

The rate of reaction rises with an increase in reductant concentration and temperature, but this increase is significant in the case of small-sized nanoparticles, i.e., 12 nm, which have a high surface area and low E a. For 50 mM of NaBH 4, k for 45 nm AuNPs is 0.10728 s −1, but for 12 nm AuNPs, the value of k is 0.145 s −1, indicating that the 12 nm AuNPs have the greatest rate constant values. As the size of AuNPs decreased the E a reduced as well, i.e. Increasing gold nanoparticle size (12, 30, 45 nm) decreased rate constant. This rise was significant for the small AuNPs. The value of k increases by increasing reductant concentration. The kinetic parameters i.e., rate constant, and activation energy (k, t 1/2, E a) were determined for three distinct sizes of gold nanoparticles (AuNPs) using the reductant at various concentrations. As reaction catalysts, AuNPs maintain their optical density which shows their stability during the course of reaction. The UV–visible spectra were recorded at regular intervals, and it was seen that the peak of K 3Fe (CN 6) −3 decreased gradually with time, at the same time surface plasmon resonance of AuNPs remained constant. Spherical nanoparticles of size 12, 30, and 45 nm were observed. Transmission electron microscopy analysis is employed to investigate morphology and particle size. Comparative kinetic analysis of different sizes of AuNPs including rate constant, activation energy, Entropy values and Frequency of collisions are reported for the first time.

In this work, the catalytic activity of three different sizes of gold nano particles (AuNPs) (12, 30, and 45 nm) synthesized by the citrate reduction process studied in the conventional redox reaction of K 3Fe (CN 6) −3 to K 4Fe (CN 6) −4 using NaBH 4(reductant) at four different temperatures (5 ☌, 10 ☌, 15 ☌, and 20 ☌) and measured by UV–visible spectrophotometry.

Which reaction results in the greatest increase in entropy